If I may ask: Which editions have you played? The whole "fifth wheel" thing is largely (though not totally exclusively) a symptom of 3e, so if you skipped out on that edition or never played beyond level 6 or so, the issue may not have been apparent, but it definitely was to the community at large and to WotC.
In fact, I'd go so far as to say that the serious flaws in 3e's design dictated a good 25-50% of the design decisions in 4e: every class is good at something (no more Monks with grab-bags of features that don't mesh at all), no class can ever be good at everything (no more CoDzillas or Batman Wizards), healing is relatively easy but sharply limited (no more "Wand of CLW replaces Cleric"), "support" classes that do much more than just healing/cleansing (trying to make "the party Cleric" fun, rather than rewarding people for accepting an onerous task), all classes get non-combat resources, etc. The emphasis on a flexible, transparent combat system--and a non-combat system with a very light touch so every group could handle non-combat the way they chose to--is one of the only things I can think of, at least at 1:30 am, which can't be easily tied to a 3e "problem" that WotC wanted to solve.
Edit: In fact, if you're interested (and I wouldn't blame you if you weren't), there's a great interview on the Wizards website, where Rob Heinsoo talks specifically about all the various design things that went into 4e. He makes specific note of how 3e casters became the most important members of the party, mechanically speaking (e.g. a missing Fighter would still lead to a cancelled session if their participation were important to the story, but not simply because that character couldn't play). And he also notes that the 3e Fighter, Monk, and Bard all ended up a little lackluster over time, but that the game didn't really say that.
Mostly pre-3e, and interestingly my one campaign experience with 3e went up to 6th level before it ended in a TPK. But I have read that fighters were sensational in 3e, even at maximum level. It varies table to table. 4th Edition is like a board game. The characters are all re-configured for that. The "roles" were a barrier to entry for my players. Without them, we would have played a lot more.